Electronic marker generator



May 31, 1960 Filed May 9, 1957 M. C. VOSBURGH ET AL ELECTRONIC MARKER GENERATOR 2 Sheets-Sheet 1 May 31, 1960 Filed May 9, 1957 M. C. VOSBURGH ET AL ELECTRONIC MARKER GENERATOR *ko t 2 Sheets-Sheet 2 A ttornev ELECTRONIC MARKER GENERATOR Filed May 9, 1957, ser. N. 658,918

z claims. (cl. 17e- 6.8)

This invention refers to marker generators for cathode ray tube displays and more particularly to electronic marker generators.

Cathode ray tube displays are employed for two general types of measurements. First, the measurement of a time interval for the purpose of calibration, for plotting and -for navigation. Second, the measurement of a range and rate of change of range of a target for the purpose of precise navigation and iire control. It is often desiredl to place a visible marker on a spot within a cathode ray tube presentation, such as a set of cross hairs on a radar display to determine the coordinate position of .the

States arent spot and, at the same time, obtain control signals which are a function of the markers position.

It isalso advantageous in an entirely different iield,`as television broadcasting, to blank out or lto superimpose upon portions of a televised program matter that would appear on the picture tube.

It is therefore an object of thisinvention to provide a method for generating a marker image on the screen of a cathode ray tube.

A further object is -to provide an electronic marker image for super-position upon the signal display of the screen of the cathode ray tube. v 1Still another object is to provide an electronic marker image upon the screen of a cathode ray tube and, at the same time, project control signals which are a function of the marker position. v

' A feature of this invention is the provision for a pointer which is adapted to be moved manually across the surface of a cathode ray tube and coupled -by a mechanical linkage -to a marker pattern which moves in unison with Y the pointer between the surface of a flying spot cathode ray tube and a photo-sensitive device to generate a signal which is -fed to the screen of the cathodera/y-tube to produce thereon the image of the marker pattern.`

. VAnother feature is that the signal developedin` the photo-sensitive device by the movement of the marker pattern is amplified and compared with a reference signal to derive a signal which is used to operate the apparatus of a radar and also gun controls. A

' The above-mentioned and other features and objects of, this invention Will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

f Fig. 1 is a block diagram of one embodiment ofA this invention; l

Fig. 2 is a block diagram of another embodiment of this invention;

Fig. 3 is a view of a radar display on the screen of the cathode ray tube without the cross-hair marker;

- Fig. 4 is a view of the same display with the crosshairmarker; I

Fig. 5 is a view of the flying spot tube with the marker pattern in the same relative position as the cross-hair marker of Fig. 4; and

Fig. 6 shows lthe resulting signal when the marker signal is compared to the reference signal in twov coordinate positions. I

With reference to Fig. 1, there is shown a cathode ray display tube 1 and a flying spot scanner tube 2. A 'synchronzing generator 3 is coupled 4to the sweep generator 4 which is coupled to the cathode ray tube l and the flying spot tube 2 sothat the horizontal and vertical scanningvofboth tubes are in synchronism. The horizontal and vertical scanning-are similar to standard television display circuits with ytwo separate -sawtooths simultaneously applied to the vertical and horizontal plates of the cathode ray tube. The horizontal Vsawtooth is of short duration vwhile the vertical sawtooth is of much longer duration and the circuitry is, of course, adjustable to any desired time. A pointer 5 is attached to a marker pattern 6 by means of a mechanical linkage 7, which may be a pantograph or any other suitable linkage, to transmit the same relative motion of the pointer 5 across the surface 8 of the tube 1 to the marker pattern 6 as it moves in front of the flying spot scanner 2. On either side of the marker pattern 6 and axially of the flying spot tube 2 are two lenses 9 and 10 which serve to focus the light spot of the ilying spot tube 2 on ther marker pattern 6l and then project it on the photomultiplier 1|1. The output of the photomultiplier 111 isv then fed to the marker amplifier l12. The output of amplifier 12 s coupled to an x or narrow pulse selector 13 and a y or wide pulse selector v14. VThese pulse width selectors 13 and 14, also known as pulse discriminators, are well known and an examplethereof is described in the publication Threshold Signals, volume 24 of the M.I.T. Radiation Laboratories Series, edited by Messrs. Chance, Hulsinger, MacnicholY andV Williams, published by McGraw-Hill Book Company at pp. 363 to 365. The output of the pulse selector 13 and the horizontal synchronizing pulse output ofthe synchronizing generator 3 are coupled to the OR gate 15 such for example as is described'in the publication Pulse land Digital Circuits by Jacob Millman and Herbert Taub, published by McGraw-Hill Book Company, 1956,- at pp..394-397; Ihe output of the pulse selector 14 and the vertical synchronizing pulse output of the synchronizing circuit 3 are coupled to the OR gate 16. The pulse output of OR gates 15 and 16 are fed tox meter 17 and y. meter 18 such, for example, as provided by the Berkely 7250 time `Interval Meter, manufactured by the-Berkely Division of Beckman Instruments, Inc., Richmond, California, for instantaneous x and y coordinate determination andV are also coupled to utilization circuit 19. VThe video signal and the output of ythe marker amplifier 12 are coupled to the summing amplier 20, such, for example, as is described -in the publcation.Electronic and Radio Engineering, by F. E. Terman published by McGraw-Hill Book Company, Inc.,v fourth edition at pp. 663 to 664. The output of ampliiier`20 is coupled to Ithe cathode ray tube 1 for display on the screen thereof. j

Figure 2 shows the circuitry of lFig. 1 omitting the pulse selectors 13 and I14, gates 15 and 16, .the x meter 18, the y meter 17 and the utilization circuit 19. The output 'of the summing amplifier 20 is coupled both to the cathode ray tube 1A and a television transmitter 21. .This circuit is` adapted for those cases where only the marker image for superposition is vdesired ora portion 3 or the picture is to be blanked out, as television broadcasting, and no control circuitryI is required. f

The operation of the vinvention is as follows. The sweep generator 4 and the synchronizing generator 3 supply two identical sweeps to the deflection circuits of the cathode ray tube v1 and the ying spot scanner tube 2. The raster thus produced is a conventional television type raster without interlace, the horizontal scan rate being sonic 50G-per second4 and. the.- verticel scanzretefSO pcrfsecond. rests?. is produced-by a 5.0.0 cyclesew.n tooth waveform being applied to the, gc detiectionrplio and a.; 3Q cycle sewtooth. applied'to the. y, deectionrlefe of, the. respective tubes.: "libe, video signal fed. infn?.y 'chev dis: play tube y1 from the amplifier 20 will be displayedonlthe screen. ott-ne tube 1 and will. be scenes tbesignalspot. .22. for.- examplein the raster area 23: as shown in lli-isz 3f. The pointer 5 will be pointed. at. thespot 2.2.t and w' l in e the. marker pattern 6.. to the saine,y relative. posi` on. l1 respectto the flying spot, tube ,2., Eig. 5 shows Vthis relationship where the4 marker patternv 6 contains, the cross; hairs 24vv which are to be transmittedbythe flying spot through the photomultiplier 11, the marker-E amplifier 122.. and the amplifier 20. to appear on, the screeneo ,thegdiss play tuberv 1 as 24a. in Fig.. 4. The center ofy thefcross hairs image 24a is atthe same point, thatv is, the center of spot- 22, at which, the pointer is directed;A Alsoin Fig. 4 are shown the horizontal scanning lines 2.5.. Point 2,7 is the tirst portion off the cross hairs image. 24a which is illuminated by the scanning beam'of the cathode'f ray tube 1. To represents the. zero reference` point when time equals zero. and is the reference forbothvertical and horizontal scanning, thisref erencebeing. supplied by the vvertical and horizontal synchronizing pulsesl The horizontal scan is made much faster.f than-'the vertical scan. Whenever the raster traverses the verticalV cut 'out portion yof,y the markerpattern, 6, a short pulse .is- -pro-i duced, and whenever the raster traverses the. horizontal cut out portion of the pattern 6, a much longer-"pulseis produced. Y p i The output of the yamplifier 12 is the ampli'edf marker signal pulses produced' by the action of the yi'ng spot 2,938,949 n y j the marker vpattern 6 from the origin of the vertical sweep. may be determined. Fig. avshows the combined tube 12 on the photomultiplier 11. These signal' pulses are f ed into the amplifier 20 and combined with the video signal to produce the combinedI video signalj and marker image on the screen of the displaytube; 1f. V'Where/ signal pulse of the horizontal component as a function .of time where Tax is the reference point and the time interval between T0X and spot 27 is represented by the displacement of pulse Tzqx. The vertical component of the position of point 27 is represented in Fig. 6bwhere Tox is lche vertical reference pulse, T27 is the vertical pulse denoting point 27 and the distance between the two pulses is a measure of the elapsed time therebetween. The pulse outputs of thefgates,l 1 5 and 16 can be used in the utilization circuit-1r9 to control the tracking apparatus of the radar system and for fire control and to determine, the instantaneous. coordinate. position of the spot Y .2.2 as inthe x. and senseless. 1.8 and; 19..

we.- have. described-abo .e the -prlnciplesotr-,our invention. in, connection withspfecic.- apparatus, it is to be clearly understood. that. description is made only by way of'example and not as a limitation to the scope of our invention/as set; f ortha in; the: objects thereof and in the accompanying claims.

We claim:

1- yIn combination; a dsplarcatbode ray4 tube, means to apply video signals; to. said. cathode ray tube for dis..- play on the screen thereof, a pointer adaptedto-be moved over the surface of. said. cathode ray tube. with a um thereof pinpointinsiaseiected object in. said display; said pointer beingmovableto followY said object, a markerv` Pattern, means: coupling said. pointer. to said. marker Y pattern, to move said,n'larkerl pattern in unisonwith said pointer. as said pointer follows said,l object, means ass ciated with said marker; pattern tot generate markery sig. nals representative. of the position; of said markerpab. tern, meansv coupling said marker signals to said cathode ray: tube to `display -on the-r screen offsaidY cathode ray tube a marker indication corresponding tothe location of said pointer, the means for generating saidmarker signals, comprising photosensitive means including a ying spotcathode ray tube and a photomultiplier disposedl on' opposite sides of said marker patternto.' produce said markerv signals,'said flying.y spot cathode rayitube further comprising a synchronizing source. and scanning means,

' said marker signals comprising short pulses indicative that is the only requirement ofthe system as-inteleu vision broadcasting, previouslyfmentioned, 'noother-use is made of the output signal of the amplifier 12.V` How-` ever,V in radar tracking and,v associated tire control, there is required indications ofj the` marker positionv as` aglunction of time. Therefore, in these cases, thefoutputeof y the amplifier 12 issplit up into its component parts,' 'that is, the short pulse or x component and the long pulse or y component, The x component pulse'is much shorter than the. y component. Pulse., so that, separation of the 'two pulses can. ybe mede. tlicennlse selectors 13 and 14:y After passing through the pnlsej selectors-13 and 14., the pulses are compared in. time. relationship. with the. x. and y reference synchronizing pulses.. in. the 0R gates, 15 and 16 and the, outputs. *thereofe4 are; obtained, v'vhich'V are. shownin Eig, 6.-k In otbcr'words. tnepulses now separated may be used as, mark s, when 'ref ferred. against the vertical. andi horizontal: scanning'signals to indicate the position of. the markerpstlern Withi te@ speci; to the scanning resten The. horizont can duree tion is. npprozn'inately.'Y 2.00.0. mi.croseconris.;Y sween.; When a gate (which is included in'each; meter; ljf'and 18) is opened at the beginning of` thesweep and; closed at the time of generationv of the short. pulse atY the' x pulse selector.: 13 and the ynumber of clock: pulses passed by thegate counted, the count willv be. proportional to the distance of the vertical bar in thev marker.- patterni 6 from the vorigin off the'I horizontal sweep. Similarly, a measurement ofdisplacementlot?,thel horizontalportion. or,

of the x coordinate position of saidobject andy long pulses indicative of the y coordinate position oisaidl ob-` ject and means coupled to said marker signals andsaid synchronizing` source to determine the location of said object. y" L n Y' f 2'.In combination; a display cathode ray tub ermeans to apply video signals to said cathode ray? tubetor `display on the screen thereof, a pointer adapted.' tobe moved over the Vsurface ot said cathode rayI tubeA with l a part thereof pinpointing a Selected' objectV in said display, said pointer being lni -'ab1e to follow said obiectl .a marker Pattern,` means couplingY said Pointer to.` said marker pattern to. move said markenpatternin; ngnisori.v With said; nointer. assaidpointer follows said object.. means associated.' Wit-.h said. markerpatternto generate marker signals representative of the 'positionfiof'r 'said marker. pattern, means coupling. said. marker signals.. to said, cathode.- reu'.v tube. to. displfa on the screenoi said ,cathode ray tube a marker. indication corresnondine-io the.. location of said pointer. themeans for, generating-said marker signals, comprising nhorosensitive. meansginclnds ing, ya flying spot cathode ray tube. and a. nhotoninltiglier, disposed on opposite. sides oi saidv snai-ker pattern to produce. said; marker signals, Vsaid ilyingV spot cathode ray tube further comprising a synchronizing sourceanl scanning means,Y marker signals oonflprisinsI short pulses' indicative of the x coordinate position of saidlbject and long. pulses; indicatiye. ofA the .y1 coordinate. Position. of

5 6 separating means and to said synchronizing sources to 2,622,240 Fleming-Williams Dec. 16, 1952 compute the elapsed time of occurrence of said short 2,636,166 Herbst Apr. 21, 1953 pulses and said long pulses and thereby determine the location of said object. FORMS-Ht: PATENTS 5 750,628 Great Britain June 20, 1956 References Cited in the le `of this patent OTHER REFERENCES UNITED STATES PATENTS -Radio Engineering, third edition, by 1F. E. Terman, 2,513,490 JOnES July 4, 1950 published by McGraw-Hill Book CO., Inc. 1947, Page 

